RAID (redundant array of independent disks) is a data storage virtualization technology, which combines a plurality of physical disk drives into a single logic unit for the purposes of data redundant backup and/or performance improvement. With RAID 5 as an example, it may include block-level stripes having distributed check information. When a single disk fails, the subsequent reading can be calculated through the distributed check information, such that no data will be lost. Meanwhile, a spare disk will be selected to replace the failing disk, and all data on the failing disk will be rebuilt and written onto the spare disk. Because in the conventional RAID, an RAID group (RG) will consume all disk space within this group, which will cause the following problems: (1) if a single disk fails, the write input/output (10) for rebuilding will be directed to a unique spare disk; therefore, bandwidth of the spare disk will become a bottleneck for rebuilding performance. (2) user IOs for a same RG will be affected seriously, and response time of these user IOs will increase significantly, because IO performance of the RG is limited by the slowest disk of this RG; and in the case of rebuilding, the disk in the rebuilding will limit the user IO performance. (3) Because disk capacity increases yearly, the two problems above are magnified, thereby causing a larger risk of data loss to the user.
A next generation RAID technology (also referred to as “mapped RAID technology”) may be introduced to solve the problem above. The mapped RAID may include more disks than conventional RAIDs. When creating the RAID stripes, a plurality of disk segments may be randomly selected from a plurality of disks, such that the data and check information are finally distributed in all disks. When one disk fails, for each disk segment on the failing disk, one disk segment on other disks may be randomly selected as an alternative. Therefore, with this technology, all disks will be involved in the rebuilding process. Because a single spare disk does not exist and writing in a plurality of disk segments can be executed in parallel, the entire rebuilding time will be decreased.
However, due to the complexity of the model of mapped RAID, it is an issue regarding how to evaluate its rebuilding performance before implementation. Besides, the Chinese patent application No. 201610103823.6 entitled “Method and Device for Guaranteeing Reliability of Redundant Array of Independent Disks,” which was filed on Feb. 25, 2016, mentioned a relationship between rebuilding rate of the mapped RAID, the number of disks and its reliability. Therefore, a problem to be solved in the art is to determine, for a specific mapped RAID model, whether its rebuilding performance can satisfy its requirements of reliability.
Therefore, there is needed a more efficient solution for evaluating rebuilding performance of RAID in the art to solve the problem described above.